Gate 3 - Group 4

Gate 3: Product Analysis

Purpose

With our hammerdrill now fully dissected, we can now complete a detailed analysis of it. Here in Gate 3 we will examine the product at the component and subsystem level, while gathering detailed information of its form and functionality. Specifically, in the section of the project, we will document a parts list, analyze several individual components, provide solid-modeled assembly drawing of a few of our parts, analyze a function/mechanism present in out product, and also recommend a few design changes.

Project Management: Coordination Review

Cause for Corrective Action

Our goup management has not been confronted with any new, unexpected problems, in addition to those mentioned in previous gates. We have concluded how extremely difficult it is for all four members to meet together outside of class time, due to personal schedules, yet we have still succeeded in combining our efforts to complete project work. While keeping in close contact via email and text messaging, we have found it most beneficial to evenly distribute the work amongst the group members, by collectively determining who is best suited to complete certain tasks. While each member has had their schedules filled with other homework, exams, and working several days a week, careful planning and time management has proven beneficial for the completetion of gates thus far.

Product Archaeology: Product Evaluation

Parts List/Component Summary

Component #	Part Number	Component Name	Amount Required	Component Function	Material	Manufacturing Process	Image Guide
1		Torx Screw			Steel, Black Oxide Finish
2		Torx Screw			Steel, Black Oxide Finish
3		Torx Screw			Steel, Black Oxide Finish
4		Torx Screw			Steel, Black Oxide Finish
5		Torx Screw			Steel, Zinc Finish
6		Lag Bolt, Hex Head, 3/8" X 4 1/2"			Steel, Zinc Finish
7		Side Handle			Plastic, Black
8		Handle Clamp			Aluminum
9		Chuck Assembly			Plastic, Stainless Steel
10		Gear Assembly
11		Bearing, Ball			Stainless Steel
12		Baffle			Plastic, Black
13		Selector Assembly			Plastic, Black
14		Plug			Rubber, White
15		O Ring Seal			Rubber, Black
16		Brush Assembly, Right			Plastic Black, Copper, Steel
17		Brush Assembly, Left			Plastic White, Copper, Steel
18		Armature			Steel, Copper, Ceramic
19		Field			Steel Copper
20		Trigger Assembly, Variable Speed, Reversable			Plastic Black, Steel, Copper
21		Field Case			Plastic, Yellow
22		Handle Cover			Plastic Yellow, Rubber Black
23		Power Cord, 18 Gauge, 2-Wire			Rubber Black, Copper
24		Chuck Key			Black Oxide Waxed Steel
25		Key Holder			Rubber, Yellow

Product Analysis

Component Complexity Scale

Component Complexity Level:	Description:
1	Constructed using only one manufacturing process, consists of a single material, easily designed and fabricated.
2	Constructed using two or three manufacturing processes, up to three different materials, more difficult to design and fabricate.
3	Constructed using four or more manufacturing processes, one or more different materials, most difficult to design and fabricate.

Interaction Complexity Scale

Interaction Complexity Level:	Description:
1	Interactions are not complex or just physically fastened, no flows.
2	Interactions are moderately complex, at least one flow.
3	Interactions are very complex, 2 or more flows.

1st Component: Field Casing

• Component Function
  

The predominant function of the field casing is to protect the inner components of the drill and provide a solid outer shell for the drill. The field casing is comprised of two identical halves fastened together by several screws. The inner parts and components of the drill such as the armature,field and gear assembly are all contained within the upper part of the field casing. The lower handle portion of the field casing houses the trigger assembly. The handle provides the user with the ability to use the drill. Without this ergonomically designed handle, the user would not be able to easily grip and use the drill. Human energy is inputted into this component. This form of energy is responsible for keeping the drill in position to best complete the task designated by the user. The drill housing operates in a standard atmosphere, up to a certain temperature to prevent deformation. The field casing can operate and perform well in any practical environment. Obviously the drill would not be used somewhere that was hot enough to melt the plastic the field casing is made of.

• Component Form
  

Field Casing

The field casing is in the shape of an L with many different contours. The right and left sides of the casing are similar in shape, but are not completely identical due to the way the components on the inside are arranged. The field casing is primarily three dimensional in order to house the internal components. The shape of the field casing is also influenced by the assembly of the internal components. The components are arranged on the inside of the drill to minimize the internal volume. The handle provides ergonomic grooves for fingers. The drills field casing is the largest component of the drill. However, it is very light compared to its size. It is about a pound. The housing is made out of plastic. The manufacturing process used to make the field casing is injection molding. The material often used in injection molding is plastic. The field casing must be strong enough to protect the inner components from drops and falls and normal use of the drill. Plastic is pretty durable and cheap so it is well suited to protect the inner components of the drill and it will not effect the overall price of the drill to much. Injection molding is very cheap to use to create mass quantities of parts. The plastic used to make the field casing can be recycled at the end of the drills life cycle. Aesthetically, the drill housing has a very basic appearance. It is yellow in color with a black patch and yellow lettering. The drill casing has a dull and slightly rough finish. The functional purpose of this finish is to help prevent slippage of the users hand.

• Manufacturing Methods
  

• Component Complexity:
  

Level: 1

The single manufacturing process used is injection molding. Two injection molds are used in the production. One for the left and right sides. The single material used is plastic. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 1

• The field casing of the drill holds all the inner components of the drill in place by fitting them into the slots defined by the molding of the casing. The right and left sides of field casing are fastened together by screws.

2nd Component: Power Cord

• Component Function
  

The predominant function of the power cord on the hammer drill is to bring electrical energy into the drill. All the components inside the drill need electrical energy provided by the power cord. The electrical energy is imported to the system through the power cord and is converted to rotational energy by the motor. The power cord is plugged into the wall using human energy. The power cord can only operate in an environment where there is an electrical power outlet. Part of the electrical cord is also housed inside the field casing. This is where the wires are connected to the trigger. This is how the human controls the input of electrical energy to the system.

• Component Form
  

Chuck key

The power cord is made of a flexible and durable rubber allowing it to be bent and folded into any shape. The cord is primarily cylindrical in shape. The cord is about one centimeter thick. At the end of the cord is a 3 prong wall adapter. Due to the flexibility of the cord, the drill can be used around any obstacle. The metal prongs on the wall adapter transfer electrical energy from the power outlet to the drill. The cord is very light. It weighs about a pound. The outer layer of the cord is made of rubber. This rubber protects the copper wire inside that transfers the electrical energy to the drill.The rubber outer layer acts as an insulater on the copper wire making it safe to touch the power cord while it is plugged into the wall.The inner wire had to be made of something conductive. Copper is an electrical conductor and is a relatively cheap metal. The plastic plug portion of the cord is made through injection molding which is cheap and very efficient. The plastic used can be recycled at the end of the drills life cycle. Aesthetically, the power cord is thin and black making it as unnoticeable as possible. The surface finish of the power cord is smooth and shiny making it able to slide against surfaces without damaging them.

• Manufacturing Methods
  

• Component Complexity:
  

Level: 2

More than one manufacturing process is used. Three different materials are used: plastic, rubber, copper. The number of manufacturing processes used is the biggest factor in determining the components complexity. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 2

• The power cord provides electrical energy to the system. Without this electrical energy, the system is useless.

3rd Component: Side Handle

• Component Function
  

The predominant function of the side handle is to give the user a place to hold on to the drill. This will in turn give the user more control over the drill and make the operation of the drill much safer. The side handle connects to the handle clamp which is connected to the drill. Human energy is imported from the users hand. The human energy provides stability to the drill when it is in use. The handle can operate in any practical environment. The drill would not be used in an environment hot enough to melt the plastic it is made out of.

• Component Form
  

Handle

The side handle is made of a durable non flexible plastic. The handle is three dimensional, cylindrically shaped and it flares out at both ends. The handle is 7 inches long and an inch wide at the ends. The handles shape is ergonomically designed so it easily fits into a wide variety of hand sizes. The handle is solid plastic and weighs about a half pound. Economically, the manufacturers choose to make the handle out of plastic because it is very durable, cheap and recyclable. Also, not all drills include an extra removable handle. The manufacturers included it to improve the safety of the user and bystanders. Aesthetically, the handle is very basic. It is black and has grooves in it to help provide the user with more grip and less slippage. The handle also bears the Dewalt name on it. The handles finish is shiny, smooth and has the grooves to provide more grip.

• Manufacturing Methods
  

• Component Complexity:
  

Level: 1

• One single manufacturing process is used. The single material used is plastic. The number of manufacturing processes used is the biggest factor in determining the components complexity. The number of materials used to create the component is also very important in determining the complexity of the component.

• Interaction Complexity:
  

Level: 1

• Human energy is imported onto the handle by the user to provide drill with more stability. The handle connects to the handle clamp and the handle clamp is attached to the drill.

4th Component: Handle Clamp

• Component Function
  

• Component Form
  

Handle Clamp

• Manufacturing Methods
  

• Component Complexity:
  

Level: 1

• Interaction Complexity:
  

Level: 1

5th Component: Chuck Assembly

• Component Function
  

• Component Form
  

Field Casing

• Manufacturing Methods
  

• Component Complexity:
  

Level: 1

• Interaction Complexity:
  

Level: 1

6th Component: Armature

• Component Function
  

• Component Form
  

Armature

• Manufacturing Methods
  

• Component Complexity:
  

Level: 1

• Interaction Complexity:
  

Level: 1

7th Component: Gears

• Component Function
  

• Component Form
  

Gear Assembly

• Manufacturing Methods
  

• Component Complexity:
  

Level: 1

• Interaction Complexity:
  

Level: 1

Solid Modeled Assembly

• For our solid modeled components and assembly, we decided it would be best to show the interactions between the shafts and gears which allow for the product to work correctly. The assembly we formed consists of the motor shaft, the helical gear, the gear shaft, and it's ball bearing, the shaft gear, the chuck gear, the chuck shaft, and it's ball bearing. Since the motor powers the drill, it was important to show the motor shaft interacting with the gear assembly which connects to the chuck shaft and therefore the drill bit. The motor shaft extends underneath the helical gear on the gear shaft, which also has a shaft gear on the other end. This shaft gear connects to the chuck gear above it which is held in place by the chuck shaft extending to the drill bit. The overall rotational motion in the drill bit is transferred from the motor through the shaft and gear components thus our reasoning to reveal this assembly.
• In order to draw up the described assembly in a 3D program, we chose to use Creo Parametric as our CAD package. This was a result of one of our members having previous experience with this program. They are currently taking a course which requires Creo Parametric drawings so due to this familiarity Creo was chosen.

Number of components:	Components used in assembly:
2	Ball Bearings
1	- Gear Shaft Ball Bearing
1	- Chuck Shaft Ball Bearing
3	Shafts
1	- Motor Shaft
1	- Gear Shaft
1	- Chuck Shaft
3	Gears
1	- Helical Gear
1	- Gear Shaft Gear
1	- Chuck Gear

Individual Part Drawings

Individual Part Drawings

Assembly Drawings

Assembly Drawings

Engineering Analysis

We selected the gear system for analysis, because it is an important mechanism that plays a major role in the function of this drill. Its purpose is to transfer the rotational energy of the motor to the rotational energy of the chuck/bit, by changing the RPM. In the original design process, engineers had to design a sufficient and efficient gear train to produce a desired drill bit RPM, from a given motor RPM. While disassembling and playing around with the parts, we rotated the drill chuck to see the relationship between the output and input RPM's. We discovered that the chuck actually rotates much slower than the motor shaft, and therefore expected the following calculations to agree with this observation. The designers most likely would have created an analysis similar to the following.

Problem Statement

• Given the speed of the motor (in revolutions per minute) and the sizes of gears, determine the final output speed (in RPM) of the drill bit.

Diagram of the System

(n = number of teeth on gear)

Assumptions

• 100% efficiency, no speed lost by friction
• Constant rotational velocity (neglecting accelerations to simplify calculations)
• Drill bit/chuck rotate at same velocity as final gear
• The first gear has the same rotational velocity as the motor
• Motor is running at full power
• Neglect the resistance force on drill bit from different drilled surfaces
• Gear teeth mesh perfectly (neglecting any speed loss from gaps between gears)
• (For the calculations): neglect direction of shaft/gear rotation
• Input speed from motor is 30,530 RPM
• Motor shaft and Gear #1 have same RPM
• Gear #2 and Gear #3 have same RPM
• Gear #3 and drill bit have same RPM

Governing Equations

• (w2)/(w1) = (n1)/(n2)
• Overall Gear Ratio = (Output Rate)/(Input Rate)

Calculations

(w = rotational speed; n = number of teeth on gear)

• Determine RPM of Gear #2

(w2)/(w1) = (n1)/(n2)

(w2)/(30,530 RPM) = (5 teeth)/(31 teeth)

w2 = 4924 RPM

• Determine RPM of Gear #4

w2 = w3 = 4924 RPM

(w4)/(w3) = (n3)/(n4)

(w4)/(4924) = (17)/(31)

w4 = 2700 RPM = Output Speed

• Determine overall gear ratio

Overall Gear Ratio = (Output Rate)/(Input Rate)

Overall Gear Ratio = (2700 RPM)/(30,530 RPM)

Overall Gear Ratio = 0.088

Solution Check

• All units correctly carried through
• Assumptions were appropriate and reasonable
• Resulting answer seems quite logical
• No errors were made in our calculations

Interpretation/Discussion

• The typical drill bit speed of a hammerdrill ranges from 1100 to 3000 RPM (http://www.ehow.com/facts_7707316_can-drills-used-regular-drilling.html). Our calculated output speed came to 2700 RPM, which is an acceptable value according to the given range of average values mentioned at ehow.com. We also discovered that the overall Gear Ratio is 0.088, which makes sense because we knew through intuition that the design of gear teeth ratios in this gear train would step down the motor RPM to a much lower drill bit RPM. If we calculated a much lower RPM, such as under 100, we could conclude the gear system to be unbeneficial. Such low RPM's could be achieved by basic human-powered hand tools. A much higher RPM such as 10,000 would be too much, lowering the control the user has over the drilling process. Listed below are the effects we would see if certain assumptions weren't made:

-If the drill bit/chuck did not rotate at the same speed as Gear #4, then we could not conclude the final output speed

-If the gear teeth did not mesh perfectly, then some speed would be lost, lowering the final output speed

-If we didn't ignore resistance forces, the calculations would have been much more complex, and would have lowered the final output speed

-If the motor wasn't running at full power, then the output speed would be much lower

For the sake of our calculations however, all the assumptions were very reasonable, and therefore allowed us to successfully produce a logical answer.

Design Revisions

Throughout the dissection and analysis of our hammer drill, we have decided to recommend these design revisions which would improve all aspects of the drill.

• Revision 1:

Remove cord

Removing the electrical cord and replacing it with a lithium ion battery would make the drill much more convenient for the user. Also, making the hammer drill cordless makes it much safer to operate. It eliminates the risk of the user or bystanders tripping over the electrical wire. Also, by making the drill cordless, the user unbounded as far as where they can operate the drill. The user wouldn't have to be within a few feet of an electrical outlet. Economically, cordless drills on average cost 40-50 dollars more than corded drills. The concern that cordless drills output less power than corded drills wouldn't be a concern to everyone. Many consumers may find the convenience of the drill being cordless to outweigh the power loss.

• Revision 2:

Add LED Light

Adding an LED light to the hammer drill would make the drill much more convenient to use. It would give the user the ability to operate the drill in an environment with little or no lighting. Also it would increase the precision of the drill by being able to see exactly what your drilling, which would in turn increase the users safety. Economically, adding an LED light would not add much to the overall price of the drill. LED's are very cheap.

• Revision 3:

Add Knuckle Guard

Adding a knuckle guard to the removable handle that clamps to the drill would significantly increase the safety of the user. While the user is operating the hammer drill, shard of debris may be shot up toward the drill and the user. Adding the guard would protect the users hand on the handle while they are operating the drill. In order to address economic concerns, the guard would be made of plastic so it would be cheap and easily made. Also, since it is made of plastic, it can be recycled at the end of the drills life cycle.

• Revision 4:

Add Internal Chuck Key Storage

Adding a slot on the bottom or top back of the drill where the user could store the chuck key would be much more convenient than the current system for chuck key storage. Currently, the chuck key is attached to the drill with the rubber key holder. This is a huge design flaw. Not only is the key dangling off the side of the drill annoying to the user, it is unsafe. The chuck key would be designed to slide into the drill and lock in until the user decided they needed it. This would eliminate the need for the rubber key holder and reduce the price of the drill. Also, if the user decided they didn't want to hang the key on with the rubber holder, they may remove it and accidentally lose it causing them to have to pay to replace it. Having convenient storage for the key would eliminate this from happening.